Magnetic flow
Using force lines, one can not only show the direction of the magnetic field, but also characterize the magnitude of its induction.
We agreed to conduct the lines of force in such a way that through 1 cm2 of the area, perpendicular to the induction vector at a certain point, the number of lines passed equal to the induction of the field at this point.
In the place where the induction of the field is greater, the lines of force will be thicker. And, conversely, where the induction of the field is smaller, less often, and the lines of force.
Thus, by the density of the lines of force of the magnetic field, the magnitude of the vector of its induction is judged, and in the direction of the lines of force, the direction of this vector is judged.
Observation of the magnetic spectra of a direct current and a coil shows that with the removal of the conductor, the induction of the magnetic field decreases, and very quickly.
A magnetic field with unequal induction indifferent points is called non-homogeneous. A non-homogeneous field is the field of rectilinear and circular current, the field outside the solenoid, the field of a permanent magnet, etc.
A magnetic field with the same induction in allpoints is called a homogeneous field. Graphically, the magnetic homogeneous field is represented by lines of force, which are equally spaced parallel straight lines.
An example of a homogeneous field is a field inside a long solenoid, and also a field between closely spaced parallel, flat pole pieces of an electromagnet.
The product of the induction of the magnetic field penetrating this circuit into the area of the circuit is called the magnetic flux of magnetic induction, or simply the magnetic flux.
Definition gave him and studied its properties English physicist - Faraday. He discovered that this concept allows us to more deeply consider the unified nature of magnetic and electrical phenomena.
Denoting the magnetic flux by the letter Φ, the area of the contour S and the angle between the direction of the induction vector B and the normal n to the area of the contour α, we can write the following equality:
Ф = В S cos α.
A magnetic flux is a scalar quantity.
Since the density of the lines of force of an arbitrary magnetic field is equal to its induction, the magnetic flux is equal to the entire number of lines of force that permeate the given contour.
With a change in the field, the magnetic flux that pierces the contour also changes: when the field strength increases, it increases, with attenuation decreases.
For the unit of magnetic flux in the SI systema stream that penetrates the 1 m² site in a magnetic uniform field, with an induction of 1 Vb / m², is located perpendicular to the induction vector. Such a unit is called a Weber:
1 WB = 1 WB / m² ˖ 1 m².
A variable magnetic flux generatesan electric field having closed field lines (a vortex electric field). Such a field is manifested in the conductor as an action of extraneous forces. This phenomenon is called electromagnetic induction, and electromotive force, which occurs in this case - EMF induction.
In addition, it should be noted that the magnetic fluxmakes it possible to characterize the whole of the magnet (or any other sources of the magnetic field) as a whole. Consequently, if the magnetic induction makes it possible to characterize its action at any single point, then the magnetic flux is entirely. Ie, we can say that this is the second most important characteristic of the magnetic field. So, if the magnetic induction acts as a force characteristic of a magnetic field, then the magnetic flux is its energy characteristic.
Returning to the experiments, we can also say that,that every turn of the coil can be imagined as a separate closed loop. The same circuit through which the magnetic flux of the vector of magnetic induction will pass. In this case, an induction electric current will be noted. Thus, it is under the influence of magnetic flux that an electric field is formed in a closed conductor. And then this electric field forms an electric current.
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